The invention relates generally to the area of numerically controlled machines, specifically, the invention provides a method for utilizing a sensing element on a machine to detect a workpiece characteristic and modify the execution of operational steps in a machining program.
In utilizing the earliest numerical controls, a part programmer using a drawing of the finished part was required to program every machining motion sequentially thereby creating a machining program having a series of operational steps. A number of programming aids were subsequently developed. The most important was the development of part programming languages which allowed the programmer to describe the part in primarily geometric terms, and a programmed computer converted the programmers description into a machining program which could be directly utilized by a numerical control. However, the execution of the machining program still was basically sequential in nature. Numerical control manufacturers have provided other programming aids in the form of modal commands. These allow the programmer to define the parameters of an elementary machining process, and the numerical control creates the sequences of machine motions required to execute the cycle. Again, the operational steps of the program are effected sequentially. There is one numerical control option which can alter the strict sequential nature of the program execution--block delete. In this case, a part programmer precedes an operational step with a block delete code; and a block delete switch under control of the machine operator can be turned on or off to selectively execute the coded operational step. However, except for this minor variation, the overall sequential nature of the machining program remains.
Historically, there was no need or reason to deviate from the basic sequential operation. More recent developments in the area of workpiece sensors can now provide workpiece data that was heretofore unavailable during the machining process. Workpiece sensors can now determine if a part exists, its exact location relative to the cutting tool, what type of part it is within a family of parts, if it is dimensionally within tolerance and the presence of other workpiece characteristics. Consequently, the need exists to modify the traditional sequential operation of a machining program to accommodate and utilize the additional data that can be collected during the machining process.
For example, a machining program may be written which describes every machining operation of the most complex member in a family of parts. If a less complex member of the part family is loaded on the machine, the workpiece sensor can be used to identify that particular part and efficiently machine the part by skipping all unnecessary operational steps, i.e. the machining program can be executed in a logical, but non-sequential fashion.
In another example, if a workpiece must contain a particular characteristic, e.g. a core hole, to enable the execution of other operational steps, the workpiece sensor can determine whether the hole exists, and, if necessary, cause the hole to be drilled, thereby executing a nonsequential series of operational steps in the machining program.
In another example, if the workpiece sensor detects that the workpiece is absent or is dimensionally out of tolerance, the remaining machining program can be skipped.
There are many applications where it is desirable to improve the efficiency of the machining process by modifying the executional sequence of operational steps in the machining process. The object of the claimed invention is to allow the part programmer to use a programmably controlled sensing element and execute operational steps in the machining program on a conditional basis depending on sensed workpiece characteristics.